PERMFILE47383 - Laserfiche WebLink

Home Browse Search

2.05 APPLICATIC3~1 FOR PERt~IIT FCR SURFACE Cat UNDERC~OUfID MINIIQG ACPIVYTIFS - MINIId[kf REQUZRII~ffiP!'S FCH2 OPERATIC.N AND RtCf,AMP,TION PI,AI0.5. 2.05.6 Mitigation of Surface Opal Mining Operation Il[rpacts. (COnt'd.) (3) (b) (iij (A & Bj (Cont'd.) Trailer location (see Volume 8, Map No. 8-2, and Volume 8, pages SAE-21 thru SAE-25). Flow from the site is filtered through the naturally occurring vegetative filter below the site. The vegetative filter area is undisturbed, consists primarily of dense oak brush with a grass understory, and has acxwnulated a thick, nearly continuous layer of litter and detritus. Cover in the vegetative filter area is conservatively estimated at 70%. No mixing of surface drainage and underground mine drainage occurs within or results from this small area exemption. The Sedcad modelling utilized to describe this site predicts runoff from the site will occur in compliance with the allowable settleable solids concentration. 5) Orchard Valley Mine Silo Area Railroad outslope -consisting of approximately 1.5 acres of revegetated disturbance occupying outslopes of the railroad embarilanent developed at the train loadout facility (see Volume 8, Map No. 8-3, and Volume 8, pages SAE-26 thru SAE-3o). Flay from this area travels through a grass filter established below the site. The grass filter consists of the toe of outslopes of the railroad embankment developed at the train loadout facility (see Volume 8, Map No. 8-3, and Volume 8, pages SAE-26 thru SAE-30). Flora from this area travels through a grass filter established below the site. The grass filter consists primarily of Smooth Brome and is established on the perimeter of an irrigated orchard. Cover in the grass filter area is conservatively estimated at 50%. VYass filter model inputs describing 3" spacing and 6" height are typically exceeded by the vegetation at this location. No mixing of surface drainage and underground mine drainage occurs within or results from this small area exemption. The Sedcad modelling utilized to describe this site predicts runoff from the site will occur in compliance with the allowable settleable solids concentration. 6) Orchard Valley Mine Fan Level - consisting of approximately 2.8 acres of disturbance previously approved as a small area exemption (see Volume 8, Map No. 8-lA) . COVCC agrees to provide an analytical demonstration that the area does not contribute noncompliant sediment loads to the surrounding drainages. This demonstration will entail the installation of silt fences in appropriate locations belay the area of disturbance and the subsequent sampling of runoff events. The silt fences will be examined periodically and maintained to ensure adequate function at all times. Samples will be analyzed for compliance with the NPDES settleable solids standard when measurable runoff occurs at designated sampling points in response to precipitation events of less than 10-year, 24 hour magnitude. No mixing of surface drainage and underground mine drainage occurs within or results from this small area exemption. TR 92-20 Revised 11/20/92 113b